Isolation and Characterization of Antimicrobial Alkaloids from Plumeria alba Flowers against Food Borne Pathogens

Abstract

Many plants have been identified for their applications in preventing food pathogens but identification of active compounds are yet to be defined in most cases. The objective of this study was to explore the potential alkaloids from Plumeria alba and their activity against food pathogenic and spoilage microorganisms. A total of six food borne pathogens namely Bacillus cereus ATCC 10876, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, Salmonella typhimurium MTCC 3224, and Shigella flexneri ATCC 12022 were tested against the alkaloid extract from P. alba flowers under in vitro conditions. Antibacterial assay was evaluated using well diffusion assay and minimum inhibitory concentration (MIC) values were tested by broth microdilution method. Alkaloid profile of the extracts was determined by gas chromatography-mass spectroscopy (GC-MS). Minimum inhibitory concentration (MIC) values revealed that Shigella flexneri ATCC 12022 was found to be the most sensitive organism (7.5 µg ml-1) followed by Staphylococcus aureus ATCC 6538 (15 µg ml-1). Escherichia coli ATCC 8739 was more resistant to the extract with an MIC value of > 60 µg ml-1 . Examination of the alkaloid profile of Plumeria alba flowers using gas chromatography-mass spectrometry resulted in the presence of 11 alkaloids of which 3 isoquinoline alkaloids, 2 pyridine alkaloids, 1 indole alkaloid, 1 vinca alkaloid and 1 resperine alkaloid were identified. According to the results, S. flexneri was found to be the most susceptible organism and it can be concluded that formulation of antimicrobial drugs containing P. alba flower extract to control food borne pathogens is feasible.